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What is Adverse Childhood Experiences?

A set of childhood exposures — abuse, neglect and household dysfunction — that show a graded association with poorer health, mental health and social outcomes in adulthood. Widely adopted in policy, and widely misused at the individual level.

From the PsychologyOrbit knowledge base, last updated 2 November 2026.

Knowledge base Updated 2 November 2026 2 views

Adverse Childhood Experiences

A set of childhood exposures — abuse, neglect and household dysfunction — that show a graded association with poorer health, mental health and social outcomes in adulthood. Widely adopted in policy, and widely misused at the individual level.

Definition

The original ACE study counted ten exposures before age 18: physical, emotional and sexual abuse; physical and emotional neglect; and household parental separation, domestic violence, substance misuse, mental illness and incarceration.

The score is a simple unweighted count, from 0 to 10. Its strength is that the dose-response relationship it shows is clear. Its weakness is that it treats a decade of sexual abuse and a parental divorce as one point each.

History

Felitti and Anda's study, conducted with over 17,000 Kaiser Permanente members in California between 1995 and 1997, reported graded associations between the count and a long list of adult outcomes including heart disease, cancer, depression and suicide attempt.

The finding moved into public health, education and criminal justice policy faster and more completely than almost any other psychological result of its era.

Theory

Two mechanisms are usually proposed.

Biological embedding: chronic activation of stress-response systems in development alters HPA axis regulation, immune function and brain development, producing durable changes in risk.

Behavioural pathways: adversity increases health-risk behaviours, which then produce disease.

The evidence supports contributions from both. The toxic stress framing that has dominated policy language is a useful shorthand but overstates how well the biological pathway is specified in humans.

Research

The associations are real, graded and replicated in many countries. High counts are associated with materially elevated risk across a wide range of outcomes.

The important qualifications:

  • Retrospective self-report. Prospective and retrospective measures of the same childhood adversity agree poorly — one major study found agreement close to chance for some exposures — and they predict different outcomes. Retrospective report predicts mental health outcomes more strongly, which raises the possibility that current state shapes recall.
  • Confounding. ACEs cluster with poverty and with parental characteristics that are themselves heritable and themselves predictive.
  • Prediction at the individual level is poor. A screening review found the score has low sensitivity and specificity for predicting any individual outcome. It works as a population-level signal, not as a test.

Applications

Population-level public health planning, service commissioning, and trauma-informed practice in schools, healthcare and justice settings.

Universal ACE screening is not supported by the current evidence, and several bodies have advised against it: the score does not predict well enough for an individual, there is no established intervention triggered by a given score, and disclosure without a service to follow it can cause harm.

Criticism

  • Individual prediction is weak and the score is used as a risk instrument anyway.
  • The count is unweighted, which is indefensible on the evidence about severity and chronicity.
  • The original sample was not representative: insured, largely white, middle-class Californians.
  • What it omits — poverty, racism, bullying, community violence, war, displacement — is arguably as predictive as what it includes.
  • Deterministic framing. Presenting a high score as a fixed destiny is both false and harmful; most people with high counts do not develop the outcomes.

References

  • Felitti, V. J., et al. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. American Journal of Preventive Medicine, 14(4), 245-258.
  • Baldwin, J. R., et al. (2019). Agreement between prospective and retrospective measures of childhood maltreatment. JAMA Psychiatry, 76(6), 584-593.
  • Baldwin, J. R., et al. (2021). Population vs individual prediction of poor health from results of adverse childhood experiences screening. JAMA Pediatrics, 175(4), 385-393.
  • Anda, R. F., Porter, L. E., & Brown, D. W. (2020). Inside the adverse childhood experience score: Strengths, limitations, and misapplications. American Journal of Preventive Medicine, 59(2), 293-295.
Written for PsychologyOrbit and reviewed before publishing. It is a summary for professionals and students, not clinical guidance, and it is not a substitute for the primary sources listed above.